file_r02.cpp

来自「在c环境下的对数据结构进行讲解,包含有例题及答案」· C++ 代码 · 共 33 行

//file_r02.cpp
#include <fstream.h>
#include <conio.h>					//getch()
void main()
{ int data,n, filesize;
  char ch;
  ifstream infile;
  infile.open("random.dat",ios::in|ios::out|ios::binary);
  infile.seekg(0,ios::end);				//设置到文件尾
filesize = infile.tellg();				//求文件大小或目前位置
  cout << "目前有 " << filesize / sizeof(int) << " 个数据\n";
  do
  { cout << "输入要读取第几个:"; cin >> n;
    if ((n>0) && (n<= filesize / sizeof(int)))
  { int position = (n-1)*sizeof(int);
  cout << "position=" << position << endl;
  infile.seekg(position);
  infile.read((char*)&data,sizeof(int));
  cout << data << endl;
  }
  cout << "再读取吗(Y/N)?"; cin >> ch;
  }while ((ch=='y')||(ch=='Y'));
  cout << "文件数据如下:\n";
  infile.seekg(0);
  infile.read((char*)&data,sizeof(int));	//读取数据
  while (!infile.eof())				//EOF就结束
  { cout << data << ",";
  infile.read((char*)&data,sizeof(int));	//读取数据
  }
  cout << endl;
getch();
}